In electrophotography, an electrophotographic substrate containing a photoconductive insulating layer on a conductive layer is imaged by first uniformly electrostatically charging a surface of the substrate. The substrate is then exposed to a pattern of activating electromagnetic radiation, such as, for example, light. The electromagnetic radiation selectively dissipates charge in illuminated areas of the photoconductive insulating layer while leaving behind an electrostatic latent image in non-illuminated areas of the photoconductive insulating layer. This electrostatic latent image is then developed to form a visible image by depositing finely divided electroscopic marking particles on the surface of the photoconductive insulating layer. The resulting visible image is then transferred from the electrophotographic substrate to a necessary member, such as, for example, an intermediate-transfer member or a print substrate, such as paper. This image developing process can be repeated as many times as necessary with reusable photoconductive insulating layers.
In image-forming apparatus such as copiers, printers, and facsimiles, electrophotographic systems in which charging, exposure, development, transfer, etc., are carried out using electrophotographic photoreceptors have been widely employed. In such image-forming apparatus, there are ever-increasing demands for speeding up of image-formation processes, improvement in image quality, miniaturization and prolonged life of the apparatus, reduction in production cost and running cost, etc. Further, with recent advances in computers and communication technology, digital systems and color-image output systems have been applied also to the image-forming apparatus.
Electrophotographic imaging members (such as photoreceptors) are known. Electrophotographic imaging members are commonly used in electrophotographic processes having either a flexible belt or a rigid drum configuration. These electrophotographic imaging members sometimes comprise a photoconductive layer including a single layer or composite layers. These electrophotographic imaging members take many different forms. For example, layered photoresponsive imaging members are known in the art. U.S. Pat. No. 4,265,990 to Stolka et al. describes a layered photoreceptor having separate photogenerating and charge-transport layers. The photogenerating layer disclosed in Stolka is capable of photogenerating holes and injecting the photogenerated holes into the charge-transport layer. Thus, in the photoreceptors of Stolka, the photogenerating material generates electrons and holes when subjected to light.
More advanced photoconductive photoreceptors containing highly specialized component layers are also known. For example, a multi-layered photoreceptor employed in electrophotographic imaging systems sometimes includes one or more of a substrate, an undercoating layer, an intermediate layer, an optional hole- or charge-blocking layer, a charge-generating layer (including a photogenerating material in a binder) over an undercoating layer and/or a blocking layer, and a charge-transport layer (including a charge-transport material in a binder). Additional layers such as one or more overcoat layer or layers are also sometimes included.
In view of such a background, improvement in electrophotographic properties and durability, miniaturization, reduction in cost, and the like, in electrophotographic photoreceptors have been studied, and electrophotographic photoreceptors using various materials have been proposed.
Production of a number of arylamine compounds, such as N,N,N′,N′-tetra(aryl)-1,1′-biphenyl-4,4′-diamine compounds that are useful as charge-transport compounds in electrostatographic imaging devices and processes, often involves processes that are costly and/or time-consuming.
Currently, such arylamine derivative hole-transporting molecules are prepared by a process that includes an Ullman reaction. The Ullman reaction involves the reaction of an aryliodide and an arylamine that includes the use of a copper catalyst that is either ligated or not, in the presence of a base. These reactions are typically carried out for long periods of time, at highly elevated temperatures, and with large amounts of base and catalyst. The starting materials can also be very expensive.
More recently, arylamine derivative hole transporting molecules have been prepared by a process that includes a palladium-ligated catalyst in the presence of a base. See, for example, commonly assigned U.S. patent application Ser. No. 10/992,690 filed Nov. 22, 2004. By use of this ligated palladium catalyzed process, an arylamine derivative can be economically manufactured in a shorter period of time that is isolatable in suitable purity to be used for example, for application in electrophotographic photoreceptors.
However, the above-mentioned process has its drawbacks. For example, the process typically uses palladium acetate ligated with tri-t-butylphosphine and sodium t-butoxide base as a reaction catalyst. While this scheme greatly reduces the reaction time, tri-t-butylphosphine is expensive and pyrophoric (spontaneously combusts in the presence of air).
Accordingly, improved processes providing safe, cost-effective, and efficient methods for arylamine production are desired.